Microlithography is used for the production of microstructured components such as for example integrated circuits or LCDs. The microlithography process is performed in a so-called projection exposure apparatus which has an illumination system and a projection objective. The image of a mask (=reticle) illuminated via the illumination system is projected via the projection objective on to a substrate (for example a silicon wafer) which is coated with a light-sensitive layer (photoresist) and arranged in the image plane of the projection objective to transfer the mask structure on to the light-sensitive coating on the substrate.
In operation of a microlithographic projection exposure apparatus it is desirable to set defined illumination settings, that is to say intensity distributions in a pupil plane of the illumination system, in specifically targeted fashion. For that purpose, besides the use of diffractive optical elements (so-called DOEs), the use of mirror arrangements is also known, for example from WO 2005/026843 A2. Such mirror arrangements include a plurality of micromirrors adjustable independently of each other.
Various approaches are also known for setting given polarization distributions in the pupil plane and/or in the reticle in the illumination system for optimizing imaging contrast, in specifically targeted fashion. Examples are disclosed in, for example, WO 2005/069081 A2, WO 2005/031467 A2, U.S. Pat. No. 6,191,880 B1, US 2007/0146676 A1, WO 2009/034109 A2, WO 2008/019936 A2, WO 2009/100862 A1, DE 10 2008 009 601 A1 and DE 10 2004 011 733 A1.
In particular it is known both in the illumination system and also in the projection objective for a tangential polarization distribution to be set for high-contrast imaging. The expression “tangential polarization” (or “TE polarization”) is used to denote a polarization distribution in which the vibration planes of the electric field strength vectors of the individual, linearly polarized light beams are oriented approximately perpendicularly to the radius directed towards the optical system axis. In contrast the expression “radial polarization” (or “TM polarization”) is used to denote a polarization distribution in which the vibration planes of the electric field strength vectors of the individual, linearly polarized light beams are oriented approximately radially with respect to the optical system axis.